Hydroisomerization processes using pre-sulfided catalysts

ABSTRACT

The present application relates to methods for producing a lubricant base oil from a waxy hydrocarbon feed using a pre-sulfided shape selective, intermediate pore size, noble metal-containing molecular sieve catalyst. According to the present invention, a shape selective, intermediate pore size, noble metal-containing molecular sieve catalyst is pre-sulfided to provide a sulfided catalyst, wherein the molar ratio of sulfur to noble metal in the sulfided catalyst is greater than one, and a waxy hydrocarbon feed is hydroisomerized by contacting the waxy hydrocarbon feed with the sulfided catalyst at hydroisomerization conditions, to produce a lubricant base oil.

REFERENCE TO RELATED APPLICATIONS

The present application is related to and hereby incorporates byreference in its entirety U.S. patent application Ser. No. ______(Docket No. 005950-827), entitled “Hydroisomerization Processes UsingRe-Sulfided Catalysts,” which is filed herewith.

FIELD OF THE INVENTION

The present invention relates in general to the production ofFischer-Tropsch derived lubricant base oils. More specifically, thepresent invention is directed toward using pre-sulfided, shapeselective, intermediate pore size, noble metal-containing molecularsieve catalysts to produce lubricant base oils, having high viscosityindexes and low pour points, in high yield.

BACKGROUND OF THE INVENTION

Refining operations that produce large quantities of high-qualitylubricant base oils are desirable. The demand placed on refineries forproducing the high-quality lubricant base oils in the operation ofmodern machinery and automobiles is increasing. Many refining processestend to produce large quantities of lighter grade products at theexpense of producing lubricant base oil products.

It is well known in the art to produce lubricant base oils usinghydroisomerization processes. For example, U.S. Pat. Nos. 5,135,638 and5,082,986 disclose highly shape selective catalysts for hydroisomerizingwaxy feeds. U.S. Pat. No. 5,135,638 discloses that low pressurehydroisomerization dewaxing and low liquid hourly space velocity provideenhanced isomerization selectivity, which results in more isomerizationand less cracking of the feed, thus producing an increased yield.Accordingly, U.S. Pat. No. 5,135,638 discloses that the yield oflubricant base oil products obtained may be enhanced by lowering thepressure at which a hydroisomerization process is carried out.

It is also well known in the art to use base metal catalysts and noblemetal catalysts in hydroisomerization processes. These catalysts may beused on molecular sieve supports. By way of example, U.S. Pat. No.5,885,438 discloses a process for producing a high viscosity indexlubricant from a waxy hydrocarbon feed comprising catalytically dewaxingwaxy paraffins present in the feed by isomerization in the presence ofhydrogen and in the presence of a low acidity large pore zeoliteisomerization catalyst. The catalysts of U.S. Pat. No. 5,885,438comprise a noble metal hydroisomerization catalyst, such as Pt. U.S.Pat. No. 5,885,438 further discloses that platinum or palladiumcatalysts have good hydrogenation activity, but only in the absence ofsulfur.

There remains a need for effective and efficient methods for producinghigh yields of high quality lubricant base oil from a waxy hydrocarbonfeed.

SUMMARY OF THE INVENTION

Embodiments of the present invention are directed toward methods forproducing high yields of lubricant base oil from a waxy hydrocarbonfeed. In one embodiment, the method comprises pre-sulfiding a shapeselective, intermediate pore size, noble metal-containing molecularsieve catalyst to provide a sulfided catalyst. The molar ratio of sulfurto noble metal in the sulfided catalyst is greater than one. The waxyhydrocarbon feed is hydroisomerized by contacting the waxy hydrocarbonfeed with the sulfided catalyst at hydroisomerization conditions, toproduce a lubricant base oil.

In another embodiment, a process for producing a lubricant base oilcomprises contacting a shape selective, intermediate pore size,noble-metal containing molecular sieve catalyst with a sulfur-containingspecies to provide a pre-sulfided catalyst. The molar ratio of sulfur tonoble metal in the pre-sulfided catalyst is greater than one. AFischer-Tropsch waxy hydrocarbon feed is provided. The Fischer-Tropschwaxy hydrocarbon feed is contacted with the pre-sulfided catalyst tohydroisomerize the feed, and a lubricant base oil is isolated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-2 illustrate the effect on yield and viscosity index of using asulfided SAPO-11 catalyst to hydroisomerize a Fischer-Tropsch waxy feedat 1,000 psig.

FIGS. 3-4 illustrate the effect on yield and viscosity index of using asulfided SAPO-11 catalyst to hydroisomerize a Fischer-Tropsch waxy feedat different pressures.

FIGS. 5-6 illustrate the effect on yield and viscosity index of using asulfided zeolite catalyst to hydroisomerize a Fischer-Tropsch waxy feedat 1,000 psig.

FIG. 7 illustrates the effect on the iso-to-normal C₄ ratio of using anon-stream sulfided SAPO catalyst.

FIG. 8 illustrates the effect on the amounts of light hydrocarbonsproduced using a pre-sulfided SAPO catalyst.

FIGS. 9A-C illustrate the effect on yield, viscosity index, andtemperature of using a pre-sulfided SAPO catalyst to hydroisomerize aFischer-Tropsch waxy feed at different pressures.

DETAILED DESCRIPTION OF THE INVENTION

According to the method of the present invention, it has been surprisingdiscovered that pre-sulfiding a shape selective, intermediate pore size,noble metal-containing molecular sieve catalyst improves selectivity ofhydroisomerization over hydrocracking, thus increasing the yield of alubricant base oil produced. Accordingly, contacting a waxy hydrocarbonfeed with a pre-sulfided shape selective, intermediate pore size, noblemetal-containing molecular sieve catalyst produces a high yield of ahigh quality lubricant base oil.

Catalyst Sulfiding

It has been discovered that hydroisomerization selectivity (thepreference for isomerization reactions over cracking reactions) forshape selective, intermediate pore size, noble metal-containingmolecular sieve catalysts is improved when the catalyst is sulfided.According to the present invention, preferably the catalyst is sulfidedprior to conducting the hydroisomerization reaction. A noble metal isany metal that is resistant to corrosion or oxidation. A noble-metalcontaining catalyst is any catalyst containing a noble metal. Noblemetals catalysts include platinum, palladium and mixtures thereof.

According to the present invention, the shape selective, intermediatepore size, noble metal-containing molecular sieve catalyst forconducting the hydroisomerization process is sulfided. The catalyst maybe sulfided at various stages in the hydroisomerization process. Thecatalyst may be sulfided prior to conducting the hydroisomerizationreaction. According to the present invention, the process for sulfidingis termed catalyst “pre-sulfiding” if performed prior to introducing thewaxy feed into the reactor for conducting the hydroisomerizationprocess. The process for sulfiding is termed “on-stream sulfiding” ifperformed after the hydroisomerization reaction has been initiated. Theon-stream sulfiding process may be conducted concurrently with thehydroisomerization process by using a feed for the hydroisomerizationprocess that comprises the required sulfur for sulfiding. In thealternative, the on-stream sulfiding process may be conducted by pausingthe hydroisomerization reaction process, sulfiding the catalyst, andthen resuming the hydroisomerization reaction process. If thehydroisomerization process is paused, the sulfiding of the catalyst maybe conducted by the same techniques employed for pre-sulfiding of thecatalyst. The process for sulfiding is termed “re-sulfiding” if thecatalyst that was initially pre-sulfided or sulfided in a previouson-stream sulfiding step is then again subjected to a sulfiding process.The re-sulfiding may be conducted concurrently with thehydroisomerization process or by pausing the hydroisomerization process,as described above for on-stream sulfiding. According to the presentinvention, preferably the catalyst is pre-sulfided.

According to the present invention, the sulfiding of the shapeselective, intermediate pore size, noble metal-containing molecularsieve catalyst may be carried out by techniques known to those of skillin the art for sulfiding catalysts. By way of example, the catalyst maybe sulfided by contacting the catalyst with a sulfur-containing species,usually in the presence of hydrogen. Mixtures of hydrogen and hydrogensulfide, carbon disulfide or a mercaptan such as butyl mercaptan areconventionally used for sulfiding. Sulfiding may be carried out bycontacting the catalyst with hydrogen and a sulfur-containinghydrocarbon oil (called a non-spiked feedstock) such as a sour keroseneor gas oil, or it may be accomplished by adding active sulfur to thewaxy hydrocarbon feed (referred to as a sulfur spiked feedstock).

In particular, pre-sulfiding may be accomplished by techniqueswell-known to those of skill in the art. Procedures have been developedby those skilled in the art to pre-sulfide fresh catalyst charges forfixed bed reactor systems in-situ at the start of each run. Theseprocedures normally involve a gas heat up step and catalyst drying stepin the reactor vessel, followed by catalyst wetting/soaking with startupoil, and then subsequently sulfiding in a step that employs eithernon-spiked feedstock (a feedstock containing naturally occurring sulfurcompounds) or a sulfur spiked feedstock (a feedstock to which activesulfur compounds are added). Alternatively, the sulfiding step mayemploy H₂/H₂S to sulfide the catalyst in the vapor phase. Exemplarysulfiding techniques known in the art have been discussed by HarmanHallie at a catalyst symposium in Amsterdam, May 1982, and published inthe Dec. 20, 1982, issue of Oil and Gas Journal. Another descriptionappears in a paper entitled “Properties and Application of CommercialPresulfiding Agents,” by William J. Tuzynski, presented at the 1989 NPRAMeeting.

According to embodiments of the present invention, sulfiding thecatalyst comprises the addition of at least one mole of sulfur per moleof noble metal contained in the catalyst, preferably, platinum and/orpalladium. The noble metal is dispersed within the shape selective,intermediate pore size, noble metal-containing molecular sieve catalyst.It is to be understood by those skilled in the art that the number ofmoles of metal in the catalyst is calculated by computing the grams ofcatalyst times the weight percent of the metal, divided by the molecularweight of the metal. In a preferred embodiment, the molar ratio ofsulfur to noble metal is at least 3:1. In an example of this embodiment,sufficient sulfur is added in a pre-sulfiding treatment step to resultin a molar ratio of sulfur to noble metal of at least 2:1. During thecourse of the hydroisomerization process, additional sulfur is added tothe catalyst to result in a molar ratio of sulfur to noble metal of atleast 3:1. In another embodiment, the ratio is 5:1.

Generally, pre-sulfiding techniques that make use of non-spikedfeedstocks involve decomposition of sulfur compounds into H₂S, where thesulfur compounds are naturally present in a selected startup hydrocarbonfeed. The reactor temperatures in these techniques generally range fromabout 300 to 350° C. (572 to 662° F.). In contrast, pre-sulfidingtechniques that make use of spiked feedstocks can be carried out byinjecting active, sulfur-containing organic compounds into a selectedstartup hydrocarbon feed such that the injected compounds decompose intoH₂S at temperatures lower than those that would be required to decomposenaturally occurring sulfur compounds (if present). Preferred spikingagents are dimethylsulfide and dimethyldisulfide as these compoundsallow sulfiding procedures to be accomplished at temperatures rangingfrom about 250 to 275° C.

Pre-sulfiding and startup procedures are tailored to maintain thequality of the initial waxy hydrocarbon feed and reactor temperatureconditions such that the sulfiding and hydrogenation reactions do notcreate deleterious temperature conditions in the interior of catalystpellets. Such deleterious temperature conditions may result in carbondeposition or metal sintering, both of which reduce catalyst activityand thus are undesirable. The severity of the hydrogenation reactionsthat occur during the initial catalyst conditioning and sulfiding periodis limited by the quality of the initial waxy hydrocarbon feed (e.g.,the sulfur content) and reactor temperatures, which persist until thesulfiding reactions diminish or essentially stop. Present day state ofthe art techniques allow in-situ presulfiding to be initiated attemperatures below about 200° C. (392° F.) and are completed beforetemperatures are elevated above about 300° C. (572° F.).

Techniques are known for pretreating catalysts by impregnation with asulfur compound (e.g., a polysulfide, as described in U.S. Pat. No.5,786,293) before the catalysts are charged to the reactor. This istermed ex-situ presulfiding. When using ex-situ presulfiding, thecatalyst may still need to undergo drying, wetting, and conversion to ametal sulfide state in-situ within the reactor during startupprocedures. An economical method for ex-situ presulfiding of freshbatches of catalyst, which are to be added to an on-stream reactoroperating at elevated temperatures and hydrogen pressures, is disclosedin U.S. Patent Application 2002/0043483, the contents of which is herebyincorporated by reference in its entirety.

Waxy Hydrocarbon Feeds

Feeds useful in the hydroisomerization processes according to thepresent invention are waxy hydrocarbons including gas oil, lubricatingoil stock, synthetic oil, Fischer-Tropsch derived wax, oligomerizedFischer-Tropsch derived olefins, foots oil, slack wax, de-oiled wax,normal alpha olefin wax, microcrystalline wax, and mixtures thereof. Thepreferred feeds are Fischer-Tropsch derived wax, slack wax, de-oiledwax, normal alpha olefin wax, and oligomerized Fischer-Tropsch derivedolefins. Fischer-Tropsch derived waxes are especially preferredfeedstocks.

In some embodiments of the present invention it is desirable to use waxyhydrocarbon feeds containing less than 10 ppm sulfur. Accordingly, waxyhydrocarbon feeds that contain high levels of sulfur (greater than 10ppm) are preferably hydrotreated prior to the hydroisomerizationreaction to remove sulfur. Therefore, waxy hydrocarbon feeds having lowamounts of sulfur, preferably less than 10 ppm sulfur, are preferred.These low sulfur feeds include Fischer-Tropsch derived wax, oligomerizedFischer-Tropsch derived olefins, normal alpha olefin wax, and slack waxderived from hydroprocessed feeds.

The waxy hydrocarbon feed contains at least 10 wt % wax, and oftencontains greater than 50 wt % wax, and often greater than 80 wt % wax.

Fischer-Tropsch Synthesis

Preferably, the waxy hydrocarbon feed of the present invention isderived from a Fischer-Tropsch waxy feed.

In Fischer-Tropsch chemistry, syngas is converted to liquid hydrocarbonsby contact with a Fischer-Tropsch catalyst under reactive conditions.Typically, methane and optionally heavier hydrocarbons (ethane andheavier) can be sent through a conventional syngas generator to providesynthesis gas. Generally, synthesis gas contains hydrogen and carbonmonoxide, and may include minor amounts of carbon dioxide and/or water.The presence of sulfur, nitrogen, halogen, selenium, phosphorus andarsenic contaminants in the syngas is undesirable. For this reason anddepending on the quality of the syngas, it is preferred to remove sulfurand other contaminants from the feed before performing theFischer-Tropsch chemistry. Means for removing these contaminants arewell known to those of skill in the art. For example, ZnO guardbeds arepreferred for removing sulfur impurities. Means for removing othercontaminants are well known to those of skill in the art. It also may bedesirable to purify the syngas prior to the Fischer-Tropsch reactor toremove carbon dioxide produced during the syngas reaction and anyadditional sulfur compounds not already removed. This can beaccomplished, for example, by contacting the syngas with a mildlyalkaline solution (e.g., aqueous potassium carbonate) in a packedcolumn.

In the Fischer-Tropsch process, contacting a synthesis gas comprising amixture of H₂ and CO with a Fischer-Tropsch catalyst under suitabletemperature and pressure reactive conditions forms liquid and gaseoushydrocarbons. The Fischer-Tropsch reaction is typically conducted attemperatures of about 300-700° F. (149-371° C.), preferably about400-550° F. (204-228° C.); pressures of about 10-600 psia, (0.7-41bars), preferably about 30-300 psia, (2-21 bars); and catalyst spacevelocities of about 100-10,000 cc/g/hr, preferably about 300-3,000cc/g/hr. Examples of conditions for performing Fischer-Tropsch typereactions are well known to those of skill in the art.

The products of the Fischer-Tropsch synthesis process may range from C₁to C₂₀₀₊ with a majority in the C₅ to C₁₀₀₊ range. The reaction can beconducted in a variety of reactor types, such as fixed bed reactorscontaining one or more catalyst beds, slurry reactors, fluidized bedreactors, or a combination of different type reactors. Such reactionprocesses and reactors are well known and documented in the literature.

The slurry Fischer-Tropsch process, which is preferred in the practiceof the invention, utilizes superior heat (and mass) transfercharacteristics for the strongly exothermic synthesis reaction and isable to produce relatively high molecular weight, paraffinichydrocarbons when using a cobalt catalyst. In the slurry process, asyngas comprising a mixture of hydrogen and carbon monoxide is bubbledup as a third phase through a slurry which comprises a particulateFischer-Tropsch type hydrocarbon synthesis catalyst dispersed andsuspended in a slurry liquid comprising hydrocarbon products of thesynthesis reaction which are liquid under the reaction conditions. Themole ratio of the hydrogen to the carbon monoxide may broadly range fromabout 0.5 to about 4, but is more typically within the range of fromabout 0.7 to about 2.75 and preferably from about 0.7 to about 2.5. Aparticularly preferred Fischer-Tropsch process is taught in EP0609079,also completely incorporated herein by reference for all purposes.

In general, Fischer-Tropsch catalysts contain a Group VIII transitionmetal on a metal oxide support. The catalysts may also contain a noblemetal promoter(s) and/or crystalline molecular sieves. SuitableFischer-Tropsch catalysts comprise one or more of Fe, Ni, Co, Ru and Re,with cobalt being preferred. A preferred Fischer-Tropsch catalystcomprises effective amounts of cobalt and one or more of Re, Ru, Pt, Fe,Ni, Th, Zr, Hf, U, Mg and La on a suitable inorganic support material,preferably one which comprises one or more refractory metal oxides. Ingeneral, the amount of cobalt present in the catalyst is between about 1and about 50 weight percent of the total catalyst composition. Thecatalysts can also contain basic oxide promoters such as ThO₂, La₂O₃,MgO, and TiO₂, promoters such as ZrO₂, noble metals (Pt, Pd, Ru, Rh, Os,Ir), coinage metals (Cu, Ag, Au), and other transition metals such asFe, Mn, Ni, and Re. Suitable support materials include alumina, silica,magnesia and titania or mixtures thereof. Preferred supports for cobaltcontaining catalysts comprise titania. Useful catalysts and theirpreparation are known and illustrated in U.S. Pat. No. 4,568,663, whichis intended to be illustrative but non-limiting relative to catalystselection.

Certain catalysts are known to provide chain growth probabilities thatare relatively low to moderate, and the reaction products include arelatively high proportion of low molecular (C₂₋₈) weight olefins and arelatively low proportion of high molecular weight (C₃₀₊) waxes. Certainother catalysts are known to provide relatively high chain growthprobabilities, and the reaction products include a relatively lowproportion of low molecular (C₂₋₈) weight olefins and a relatively highproportion of high molecular weight (C₃₀₊) waxes. Such catalysts arewell known to those of skill in the art and can be readily obtainedand/or prepared.

The product from a Fischer-Tropsch process contains predominantlyparaffins. The products from Fischer-Tropsch reactions generally includea light reaction product and a waxy reaction product. The light reactionproduct (i.e., the condensate fraction) includes hydrocarbons boilingbelow about 700° F. (e.g., tail gases through middle distillate fuels),largely in the C₅-C₂₀ range, with decreasing amounts up to about C₃₀.The waxy reaction product includes hydrocarbons boiling above about 600°F. (e.g., vacuum gas oil through heavy paraffins), largely in the C₂₀₊range, with decreasing amounts down to C₁₀.

Both the light reaction product and the waxy product are substantiallyparaffinic. The waxy product generally comprises greater than 70 weightpercent normal paraffins, and often greater than 80 weight percentnormal paraffins. The light reaction product comprises paraffinicproducts with a significant proportion of alcohols and olefins. In somecases, the light reaction product may comprise as much as 50 weightpercent, and even higher, alcohols and olefins. It is the waxy reactionproduct (i.e., the wax fraction) that may be used as a feedstock for theprocesses of the present invention.

According to the present invention, lubricant base oils may be preparedby hydroisomerizing waxy Fischer-Tropsch reaction products. Otherprocesses that may be used in preparing lubricant base oils from waxyFischer-Tropsch reaction products include hydrotreating,oligomerization, solvent dewaxing, atmospheric and vacuum distillation,hydrocracking, hydrofinishing, and other forms of hydroprocessing.

Hydroisomerization

According to the present invention, the waxy hydrocarbon feeds aresubjected to a hydroisomerization process using sulfided shapeselective, intermediate pore size, noble metal-containing molecularsieve catalysts. Hydroisomerization is intended to improve the cold flowproperties of a lubricant base oil by selective addition of branchinginto the molecular structure. Hydroisomerization ideally will achievehigh conversion of a waxy hydrocarbon feed to non-waxy iso-paraffinswhile minimizing conversion by cracking.

According to the present invention, hydroisomerization is conductedusing a shape selective, intermediate pore size, noble metal-containingmolecular sieve catalyst. The phrase “intermediate pore size,” as usedherein means an effective pore aperture in the range of from about 4.0to 7.1 Å when the porous inorganic oxide is in the calcined form. Theshape selective intermediate pore size molecular sieves used in thepractice of the present invention are generally 1-D 10-, 11- or 12-ringmolecular sieves. The preferred molecular sieves of the invention are ofthe 1-D 10-ring variety, where 10-(or 11-or 12-) ring molecular sieveshave 10 (or 11 or 12) tetrahedrally-coordinated atoms (T-atoms) joinedby oxygens. In the 1-D molecular sieve, the 10-ring (or larger) poresare parallel with each other, and do not interconnect. Theclassification of intrazeolite channels as 1-D, 2-D and 3-D is set forthby R. M. Barrer in Zeolites, Science and Technology, edited by F. R.Rodrigues, L. D. Rollman and C. Naccache, NATO ASI Series, 1984 whichclassification is incorporated in its entirety by reference (seeparticularly page 75).

The shape selective, intermediate pore size, noble metal-containingmolecular sieve catalysts according to the present invention may bezeolitic molecular sieves, non-zeolitic molecular sieves, or mixturesthereof. Preferably, shape selective, intermediate pore size, noblemetal-containing molecular sieve catalysts are non-zeolitic.

As used herein, non-zeolitic molecular sieve refers to a molecular sievecomprising a crystalline, three-dimensional microporous frameworkstructure of tetrahedrally-bound AlO₂ and PO₂ oxide units, andoptionally one or more metals in tetrahedral coordination with oxygenatoms. Preferably non-zeolitic molecular sieves are characterized by athree-dimensional microporous framework structure of AlO₂, and PO₂tetrahedral oxide units with a unit empirical formula on an anhydrousbasis of:(M_(x)A_(y)P_(z))O₂wherein:

-   -   “M” represents at least one element, other than aluminum and        phosphorous, which is capable of forming an oxide in tetrahedral        coordination with AlO₂ and PO₂ oxide structural units in the        crystalline molecular sieve; and    -   “x”, “y”, and “z” represent the mole fractions, respectively, of        element “M”, aluminum, and phosphorus, wherein “x” has a value        equal to or greater than zero (0), and “y” and “z” each have a        value of at least 0.01.

In a preferred embodiment, metallic element “M” is selected from thegroup consisting of arsenic, beryllium, boron, chromium, cobalt,gallium, germanium, iron, lithium, magnesium, manganese, silicon,titanium, vanadium, nickel, and zinc, more preferably selected from thegroup consisting of silicon, magnesium, manganese, zinc, and cobalt; andstill more preferably silicon. As used herein, element “M” is consideredto be a component of the non-zeolitic molecular sieve.

According to the present invention, preferred shape selectiveintermediate pore size molecular sieves used for hydroisomerization arenon-zeolitic molecular sieves. Preferred shape selective intermediatepore size non-zeolitic molecular sieves are based upon aluminumphosphates (i.e., SAPO catalysts), such as SAPO-11, SAPO-31, andSAPO-41. SAPO-11 and SAPO-31 are more preferred, with SAPO-11 being evenmore preferred. SM-3 is a preferred shape selective intermediate poresize SAPO, which has a crystalline structure falling within that of theSAPO-11 molecular sieves. The preparation of SM-3 and its uniquecharacteristics are described in U.S. Pat. Nos. 4,943,424 and 5,158,665.

In another embodiment of the present invention, zeolitic molecular sievemay be used. These include ZSM-22, ZSM-23, ZSM-35, ZSM-48, ZSM-57,SSZ-32, offretite, and ferrierite, with SSZ-32 and ZSM-23 beingpreferred.

A preferred intermediate pore size molecular sieve is characterized byselected crystallographic free diameters of the channels, selectedcrystallite size (corresponding to selected channel length), andselected acidity. Desirable crystallographic free diameters of thechannels of the molecular sieves are in the range of from about 4.0 to7.1 Å, having a maximum crystallographic free diameter of not more than7.1 and a minimum crystallographic free diameter of not less than 3.9 Å.Preferably the maximum crystallographic free diameter is not more than7.1 and the minimum crystallographic free diameter is not less than 4.0Å. Most preferably the maximum crystallographic free diameter is notmore than 6.5 and the minimum crystallographic free diameter is not lessthan 4.0 Å. The crystallographic free diameters of the channels ofmolecular sieves are published in the “Atlas of Zeolite FrameworkTypes”, Fifth Revised Edition, 2001, by Ch. Baerlocher, W. M. Meier, andD. H. Olson, Elsevier, pp 10-15, which is incorporated herein byreference.

A particularly preferred intermediate pore size molecular sieve, whichis useful in the present process is described, for example, in U.S. Pat.Nos. 5,135,638 and 5,282,958, the contents of which are herebyincorporated by reference in their entirety. In U.S. Pat. No. 5,282,958,such an intermediate pore size molecular sieve has a crystallite size ofno more than about 0.5 microns and pores with a minimum diameter of atleast about 4.8 Å and with a maximum diameter of about 7.1 Å. Thecatalyst has sufficient acidity so that 0.5 grams thereof whenpositioned in a tube reactor converts at least 50% of hexadecane at 370°C., a pressure of 1200 psig, a hydrogen flow of 160 ml/min, and a feedrate of 1 ml/hr. The catalyst also exhibits isomerization selectivity of40 percent or greater (isomerization selectivity is determined asfollows: 100×(weight percent branched C₁₆ in product)/(weight percentbranched C₁₆ in product+weight percent C¹³⁻ in product) when used underconditions leading to 96% conversion of normal hexadecane (n-C₁₆) toother species.

Such a particularly preferred molecular sieve may further becharacterized by pores or channels having a crystallographic freediameter in the range of from about 4.0 to 7.1 Å, and preferably in therange of 4.0 to 6.5 Å. The crystallographic free diameters of thechannels of molecular sieves are published in the “Atlas of ZeoliteFramework Types”, Fifth Revised Edition, 2001, by Ch. Baerlocher, W. M.Meier, and D. H. Olson, Elsevier, pp 10-15, which is incorporated hereinby reference.

If the crystallographic free diameters of the channels of a molecularsieve are unknown, the effective pore size of the molecular sieve can bemeasured using standard adsorption techniques and hydrocarbonaceouscompounds of known minimum kinetic diameters. See Breck, ZeoliteMolecular Sieves, 1974 (especially Chapter 8); Anderson et al., J.Catalysis 58, 114 (1979); and U.S. Pat. No. 4,440,871, the pertinentportions of which are incorporated herein by reference. In performingadsorption measurements to determine pore size, standard techniques areused. It is convenient to consider a particular molecule as excluded ifdoes not reach at least 95% of its equilibrium adsorption value on themolecular sieve in less than about 10 minutes (p/po=0.5;25° C).Intermediate pore size molecular sieves will typically admit moleculeshaving kinetic diameters of 5.3 to 6.5 Å with little hindrance.

Hydroisomerization catalysts useful in the present invention comprise acatalytically active noble metal. The presence of a catalytically activenoble metal leads to product improvement, especially viscosity index andstability. Typical catalytically active noble metals include platinumand palladium and mixtures thereof, with platinum preferred. If platinumand/or palladium is used, the total amount of active noble metal istypically in the range of 0.1 to 5 weight percent of the total catalyst,usually from 0.1 to 2 weight percent, and not to exceed 10 weightpercent.

The refractory oxide support may be selected from those oxide supports,which are conventionally used for catalysts, including silica, alumina,silica-alumina, magnesia, titania and combinations thereof.

The conditions for hydroisomerization will be tailored to achieve alubricant base oil with specific branching properties, as describedabove, and thus will depend on the characteristics of feed used. Ingeneral, conditions for hydroisomerization in the present invention aremild, such that the conversion of wax to materials boiling between about650 and 1400° F. is maintained between 40 and 95 weight percent inproducing the lubricant base oil.

Mild hydroisomerization conditions are achieved through operating at alower temperature, generally between about 390 and 650° F. and a liquidhourly space velocity (LHSV) generally between about 0.5 and 20 hr⁻¹.The pressure is typically from about 15 to 2,500 psig, preferably fromabout 50 psig to 2,000 psig, more preferably from about 100 to 1,500psig, even more preferably about 150 psig to 1,000 psig, and even morepreferably about 250 to 600 psig. Using the sulfided, shape selective,intermediate pore size, noble metal containing molecular sievecatalysts, low pressure may provide enhanced isomerization selectivity,which results in more isomerization and less cracking of the feed, thusproducing an increased yield. Exemplary processes are described in U.S.Pat. Nos. 5,135,638, 5,246,566, and 6,337,010, the contents of which arehereby incorporated by reference in their entirety.

In addition, using the sulfided, shape selective, intermediate poresize, noble metal containing molecular sieve catalysts according to thepresent invention, the hydroisomerization process may be conducted athigher pressures while maintaining acceptable yield and quality of thelubricant base oil product. In fact, the present invention provides ahydroisomerization process which may be conducted at relatively higherpressures and achieve an acceptable yield of a high quality lubricantbase oil product. Conducting a hydroisomerization process using asulfided, shape selective, intermediate pore size, noble metalcontaining molecular sieve catalyst provides an acceptable yield of ahigh quality lubricant base oil even at relatively high pressures.Although sulfiding the catalyst improves the yield of lubricant base oilproduced when conducting the hydroisomerization reaction at bothrelatively high and relatively low pressures, the effect on yield oflubricant base oil product produced may be more pronounced whenconducting the hydroisomerization at high pressure. Since there may bedifficulties in operating the hydroisomerization process at relativelylower pressures, using the sulfided catalysts according to the presentinvention surprisingly provides a process by which thehydroisomerization may be operated at a relatively higher pressure whileachieving acceptable yield of a high quality lubricant base oil.Accordingly, in one embodiment it is preferable to conduct thehydroisomerization at relatively higher pressure (i.e., between about500 and 1,000 psig).

Hydrogen is present in the reaction zone during the hydroisomerizationprocess, typically in a hydrogen to feed ratio from about 0.5 to 30MSCF/bbl (thousand standard cubic feet per barrel), preferably fromabout 1 to 10 MSCF/bbl. Hydrogen may be separated from the product andrecycled to the reaction zone.

Solvent Dewaxing

According to the present invention, at least a portion of the lubricantbase oil produced by the hydroisomerization process may be solventdewaxed. Solvent dewaxing techniques are known in the art. Solventdewaxing may be used to remove any residual waxy molecules by dissolvingthe waxy components into a solvent such as methyl ethyl ketone, methyliso-butyl ketone, or toluene; precipitating the waxy components; andthen removing the waxy components by filtration. Solvent dewaxing hasbeen discussed in “Chemical Technology of Petroleum,” 3rd Edition, byWilliam Gruse and Donald Stevens (McGraw Hill, New York, 1960) pages566-570. See also U.S. Pat. Nos. 4,477,333, 3,773,650, and 3,775,288.

According to the present invention, solvent dewaxing may beadvantageously used to dewax at least a portion of the product from thehydroisomerization process to remove any residual unconverted waxycomponents following the isomerization step(s). The wax extracted from asolvent dewaxing process (referred to as “slack wax”), may be recycledto the hydroisomerization process of the present invention to obtaineven higher lubricant base oil yields.

Hydrotreating and Hydrofinishing

Hydrotreating and hydrofinishing are optional processing steps that mayalso be included in the processes of the present invention.Hydrotreating may be conducted on the waxy hydrocarbon feed prior to thehydroisomerization process. Hydrotreating refers to a catalytic process,usually carried out in the presence of free hydrogen, the primarypurpose of which is to remove various metal contaminants such asarsenic; heteroatoms such as sulfur and nitrogen, and aromatic compoundsfrom the feedstock. Generally, it is desirable during a hydrotreatingstep to minimize the amount of cracking of hydrocarbon molecules (i.e.,the breaking of larger molecules into smaller ones). Duringhydrotreating, unsaturated hydrocarbons are either fully or partiallyhydrogenated. The waxy hydrocarbon feed to the present process may byhydrotreated prior to hydroisomerization.

Catalysts used in carrying out hydrotreating operations are well knownin the art. See, for example, U.S. Pat. No. 4,347,121 and 4,810,357, thecontents of which are hereby incorporated by reference in theirentirety, for general descriptions of hydrotreating and of typicalcatalysts used in this process. Suitable catalysts include noble metalsfrom Group VIIIA (according to the 1975 rules of the International Unionof Pure and Applied Chemistry), such as platinum or palladium on analumina or siliceous matrix, and Group VIII and Group VIB, such asnickel-molybdenum or nickel-tin on an alumina or siliceous matrix. U.S.Pat. No. 3,852,207 describes a suitable noble metal catalyst and mildconditions for carrying out the reaction. Other suitable catalysts aredescribed, for example, in U.S. Pat. Nos. 4,157,294 and 3,904,513. Thenon-noble hydrogenation metals, such as nickel-molybdenum, are usuallypresent in the final catalyst composition as oxides, but may be employedin their reduced or sulfided forms.

Preferred non-noble metal catalyst compositions contain in excess ofabout 5 weight percent, preferably about 5 to 40 weight percent,molybdenum and/or tungsten, and at least about 0.5 weight percent, andgenerally about 1 to 15 weight percent, of nickel and/or cobaltdetermined as the corresponding oxides. Catalysts containing noblemetals, such as platinum, contain in excess of 0.01 percent metal; insome embodiments, between about 0.1 and 1.0 weight percent metal.Combinations of noble metals may also be used, such as mixtures ofplatinum and palladium.

Typical hydrotreating conditions vary over a wide range. In general, theoverall LHSV is about 0.25 to 2.0 hr⁻¹, preferably about 0.5 to 1.0hr⁻¹. Hydrogen partial pressure in hydrotreating may be greater thanabout 200 psia, preferably ranging from about 500 to 2,000 psia.Hydrogen recirculation rates are typically greater than about 50SCF/Bbl, and are preferably between 1,000 and 5,000 SCF/Bbl.Temperatures in a hydrotreating reactor may range from about 300 to 750°F. (150 to 400° C.), preferably ranging from about 450 to 600° F. (230to 315° C.).

Hydrofinishing is a hydrotreating process that may be conducted as afinal step on the lubricant base oil product in the lubricant base oilmanufacturing process. This final step is intended to improve the UVstability and appearance of the product by removing trace amounts ofaromatics, olefins, color bodies, and solvents. As used in thisdisclosure, the term UV stability refers to the stability of thelubricant base oil or the finished lubricant when exposed to UV lightand oxygen. Instability is indicated when a visible precipitate forms,usually seen as floc or cloudiness, or a darker color developing uponexposure to ultraviolet light and air. A general description ofhydrofinishing may be found in U.S. Pat. Nos. 3,852,207 and 4,673,487.Clay treating to remove these impurities is an alternative final processstep.

Oligomerization

The waxy hydrocarbon feed used in the processes of the present inventionmay include oligomerized Fischer-Tropsch derived olefins. Depending onthe conditions under which the Fischer-Tropsch synthesis is carried out,the Fischer-Tropsch condensate will contain varying amounts of olefins.Additionally, most Fischer-Tropsch condensates will contain somealcohols, which may be readily converted into olefins by dehydration. Asalready noted, the condensate may also be olefin enriched through acracking operation, preferably by thermal cracking. In one embodiment ofthe present invention these olefins may be oligomerized to produceFischer-Tropsch derived olefins. During oligomerization the lighterolefins are not only converted into heavier molecules, but the carbonbackbone of the oligomers will display branching at the points ofmolecular addition. Due to the introduction of branching into themolecule, the pour point of the products is reduced.

Oligomerization of olefins has been reported in the literature, and avariety of commercial processes are available. See, for example, U.S.Pat. Nos. 4,417,088, 4,434,308, 4,827,064, 4,827,073, and 4,990,709.Although various types of reactor configurations may be employed, thefixed catalyst bed reactor is commercially in use. More recently, amethod of performing the oligomerization in an ionic liquid media hasbeen proposed. Since oligomerization catalysts are very active and thecontact between the catalyst and the reactants is efficient, theseparation of the catalyst from the oligomerization products isfacilitated.

Oligomerization reactions proceed over a wide range of conditions.Typical temperatures for carrying out the reaction range from about 32to 800° F. (0 to 425° C.). Other conditions include a space velocityfrom 0.1 to 3 hr⁻¹ and a pressure ranging from about 0 to 2,000 psig.Catalysts for the oligomerization reaction may comprise virtually anyacidic material, such as for example zeolites, clays, resins, BF₃complexes, HF, H₂SO₄, AlCl₃, ionic liquids (preferably ionic liquidscontaining a Bronsted or Lewis acidic component or a combination ofBronsted and Lewis acid components), transition metal-based catalysts(such as Cr/SiO₂), superacids, and the like. In addition, non-acidicoligomerization catalysts including certain organometallic or transitionmetal oligomerization catalysts may be used, such as, for example,zirconocenes.

Lubricant Base Oil Products and Properties

Lubricant base oils made by the processes of the present invention areof high quality, as characterized by viscosity index and pour point ofthe lubricant base oil. Accordingly, the lubricant base oils have highviscosities, low pour points, and exceptionally high VI's.

Lubricant base oils having high viscosity indexes are desirable.Viscosity Index (VI) is an empirical, unitless number indicating theeffect of temperature change on the kinematic viscosity of the oil.Liquids change viscosity with temperature, becoming less viscous whenheated; the higher the VI of an oil, the lower its tendency to changeviscosity with temperature. High VI lubricants are needed whereverrelatively constant viscosity is required at widely varyingtemperatures. For example, in an automobile, engine oil must flow freelyenough to permit cold starting, but must be viscous enough after warm-upto provide full lubrication. VI may be determined as described in ASTM D2270-93. The lubricant base oils of the present invention have a highviscosity index ranging from about 140 to 190.

Pour point is the temperature at which a sample of the lubricant baseoil will begin to flow under carefully controlled conditions. Where pourpoint is given herein, unless stated otherwise, it has been determinedby standard analytical method ASTM D 5950-02. The lubricant base oilsaccording to the present invention have excellent pour points. The pourpoints of the lubricant base oils are between about −5 and −60° C.Preferably, the pour points of the lubricant base oils are less than −9° C., more preferably ≦−15° C., and even more preferably less than −15°C.

Cloud point is a measurement complementary to the pour point, and isexpressed as a temperature at which a sample of the lubricant base oilbegins to develop a haze under carefully specified conditions. Cloudpoint may be determined by, for example, ASTM D 5773-95. The lubricantbase oils with optimized branching according to the present inventionhave cloud points of less than 0° C.

In addition, the lubricant base oils of the present invention typicallyhave high oxidation stability, high UV stability, low volatility andexcellent low temperature properties. The lubricant base oils of thepresent invention have a kinematic viscosity between about 2 and 40 cStat 100° C. Preferably the lubricant base oils of the present inventionhave a kinematic viscosity greater than 2.6 cSt at 100° C., morepreferably greater than 3 cSt at 100° C.

The American Petroleum Institute (API) has classified base oilsaccording to their chemical composition. As defined by the API, GroupIII oils are very high viscosity index oils (>120) having a total sulfurcontent less than 300 ppm and a saturates content of greater than orequal to 90%. API Group III oils also are traditionally manufactured bysevere hydrocracking and or wax isomerization. Lubricant base oils ofthe present invention are generally classified as API Group III baseoils. When they are made from waxy feeds with a low total sulfurcontent, such as a Fischer-Tropsch feeds, the lubricant base oils willalso have a total sulfur content less than 300 ppm.

Lubricant base oils according to the present invention made fromFischer-Tropsch waxy feeds generally have total sulfur contents of lessthan about 5 ppm. Total sulfur is determined using ultravioletfluorescence by ASTM D 5453-00.

Blends

The lubricant base oils of the present invention may be used alone ormay be blended with additional base oils selected from the groupconsisting of conventional Group I base oils, conventional Group II baseoils, conventional Group III base oils, isomerized petroleum wax,polyalphaolefins (PAO), poly internal olefins (PIO), diesters, polyolesters, phosphate esters, alkylated aromatics, and mixtures thereof.

Since the lubricant base oils of the present invention have excellentcold flow properties, high VI's, and high oxidation stability, they areideal blending stocks for upgrading conventional lubricant base oils.

It is preferred that when the lubricant base oils of the presentinvention are blended with one or more additional lubricant base oils,the additional base oils be present in an amount of less than 95 wt % ofthe total resultant base oil composition.

Finished Lubricants

Lubricant base oils are the most important component of finishedlubricants, generally comprising greater than 70% of the finishedlubricants. Finished lubricants comprise a lubricant base oil and atleast one additive. Finished lubricants may be used in automobiles,diesel engines, axles, transmissions, and industrial applications.Finished lubricants must meet the specifications for their intendedapplication as defined by the concerned governing organization.

The lubricant base oils of the present invention are useful incommercial finished lubricants. As a result of their excellent VI's andlow temperature properties, the lubricant base oils of the presentinvention are suitable for formulating finished lubricants intended formany of these applications. In addition, the excellent oxidationstability of the lubricant base oils of the present invention makes themuseful in finished lubricants for many high temperature applications.

The lubricant base oils of the present invention are suitable forblending into a wide variety of finished lubricants, including but notlimited to automotive engine oils, natural gas engine oils, automatictransmission fluid, industrial gear oils, turbine oils, textile oils,heat transfer oils, hydraulic oils, paper machine oils, spindle oils,rock drill oils, pump oils, compressor oils, way oils, and metalworkingfluids. The lubricant base oils of the present invention may also beused as workover fluids, packer fluids, coring fluids, completionfluids, and in other oil field and well-servicing applications.

Additives, which may be blended with the lubricant base oil of thepresent invention, to provide a finished lubricant composition includethose which are intended to improve select properties of the finishedlubricant. Typical additives include, for example, anti-wear additives,EP agents, detergents, dispersants, antioxidants, pour pointdepressants, VI improvers, viscosity modifiers, friction modifiers,demulsifiers, antifoaming agents, corrosion inhibitors, rust inhibitors,seal swell agents, emulsifiers, wetting agents, lubricity improvers,metal deactivators, gelling agents, tackiness agents, bactericides,fluid-loss additives, colorants, and the like.

Other hydrocarbons, such as those described in U.S. Pat. Nos. 5,096,883and 5,189,012, may be blended with the lubricant base oil provided thatthe finished lubricant has the necessary pour point, kinematicviscosity, flash point, and toxicity properties. These otherhydrocarbons include base oils particularly useful in drilling fluids.By way of example, U.S. Pat. No. 5,096,883 relates to a substantiallynon-toxic base oil that consists essentially of branched-chain paraffinsor branched-chain paraffins substituted with an ester functionality, ormixtures thereof, the base-oil preferably having between about 18 andabout 40 carbon atoms per molecule and, more preferably, between about18 and about 32 carbon atoms per molecule. U.S. Pat. No. 5,189,012relates to synthetic hydrocarbons selected from the group consisting ofbranched chain oligomers synthesized from one or more olefins containinga C₂ to C₁₄ chain length and wherein the oligomers have an averagemolecular weight of from 120 to 1000.

Typically, the total amount of additives in the finished lubricant willbe approximately 1 to about 30 weight percent of the finished lubricant.However, since the lubricant base oils of the present invention haveexcellent properties including low pour point, high VI's, and excellentoxidative stability, a lower amount of additives may be required to meetthe specifications for the finished lubricant than is typically requiredwith base oils made by other processes. The use of additives informulating finished lubricants is well documented in the literature andwell known to those of skill in the art.

EXAMPLES

The invention will be further explained by the following illustrativeexamples that are intended to be non-limiting.

Each of these examples were carried out in a continuous-flow,high-pressure pilot plant designed to hydroprocess waxy hydrocarbonfeeds. The isomerization catalyst was laboratory prepared platinum onSAPO-11 and contained 15 weight percent Catapal alumina binder. Thecatalyst was crushed to 24-42 mesh prior to being loaded into thereactor. Process conditions included an LHSV of 1.0 hr⁻¹ over theisomerization catalyst, and a once-through H₂ rate of 5300 SCF/bbl. Theentire effluent from the isomerization reactor was passed directly to asecond reactor containing crushed Pt—Pd/SiO₂—Al₂O₃ hydrofinishingcatalyst, run at 450° F. and LHSV of 2 hr⁻¹. The feed used for theseexamples was a hydrotreated, Fischer-Tropsch derived wax, and theproperties of the feed (the hydrotreated Fischer-Tropsch wax) are asfollows: Gravity, API 40.3 Nitrogen, ppm 1.6 Sulfur, ppm 2 Sim. Dist.,Wt % Temperature (° F.) St/5 512/591 10/30 637/708 50 764 70/90 827/91195/EP  941/1047

In the following examples, the effectiveness of sulfiding thehydroisomerization catalyst was evaluated by measuring the 650° F.+yield(weight percent) and the viscosity index of the isomerizedFischer-Tropsch wax. It is known in the art that 650° F.+yield (weightpercent) is the weight percent of the total product boiling above 650°F., and is defined or calculated at a particular pour point.

Example 1 Hydroisomerization Using a Sulfided SAPO Catalyst at 1,000psig

This example illustrates the effect of sulfiding a SAPO-11 catalyst. InFIG. 1, the 650° F.+yield (weight percent) obtained when aFischer-Tropsch derived wax was hydroisomerized is plotted as a functionof pour point (° C.) for three situations: 1) when the SAPO 11 catalystis not sulfided prior to the hydroisomerization reaction, 2) when thecatalyst was pre-sulfided, and 3) when the catalyst was re-sulfidedafter being on-stream for 2040 hours. Each of the three experiments wasconducted at a hydrogen partial pressure of 1,000 psig.

For comparative purposes, data points at a pour point of about −15° C.may be considered. The 650° F.+yield for the un-sulfided catalyst wasabout 32 weight percent, which increased to a yield of about 50 weightpercent when the catalyst was pre-sulfided, representing an increase ofabout 18 weight percent. After re-sulfiding the catalyst, the yieldincreased an additional 15 weight percent, to about 65 weight percent.

The viscosity index was similarly enhanced with sulfiding, as shown inFIG. 2. At a pour point of −15° C., the viscosity index of thehydroisomerized wax increased from about 155 to 162 by pre-sulfiding thecatalyst, and with re-sulfiding after 2,040 hours on-stream, theviscosity index increased even further to about 172. This represents anabsolute increase of about 7 by pre-sulfiding, and about 10 withre-sulfiding.

Example 2 Hydroisomerization Using a Sulfided SAPO Catalyst at VaryingPressures

The effects of sulfiding at two different pressures (and the effects ofpressure without sulfiding), are shown in FIGS. 3 and 4. The 1,000 psigcurves in FIGS. 3 and 4 are the same as those in FIGS. 1 and 2; in otherwords, the 1,000 psig data has simply been re-plotted. Decreasing thehydrogen partial pressure from 1,000 to 300 psig duringhydroisomerization results in a 650° F.+yield increase from about 35 to68 weight percent, and an increase in viscosity index of about 155 to168. Thus, this example shows that hydroisomerization yield andviscosity index are both enhanced as the hydroisomerization pressure isdecreased.

Additionally, comparing FIGS. 1 and 2 with FIGS. 3 and 4 illustrate thatsulfiding a SAPO-11 had a larger beneficial effect at higher pressures(e.g., 1,000 psig) than at lower pressures (e.g., 300 psig). Sulfidingthe SAPO-11 catalyst had a modest effect on 650° F.+yield at 300 psig,and a modest effect on viscosity index (an increase of about 5), withinthe range of pour points plotted. Again, the pressures in this contextrefer to the hydrogen partial pressure within the hydroisomerizationreactor, although the hydrogen partial pressure is substantially thesame (or nearly the same) as the total pressure.

Example 3 Hydroisomerization Using a Sulfided Zeolite Catalyst

This example was conducted as described for Example 1, but using SSZ-32as the catalyst. FIG. 5 shows that the 650° F.+yield (weight percent)from Fischer-Tropsch wax hydroisomerized at 1,000 psig for both sulfidedand un-sulfided SSZ-32 catalysts. The yield was about 55 (at a pourpoint of −15° C.). Likewise, the viscosity index was about 175.

Example 4 Hydroisomerization Using an On-Stream Sulfided SAPO Catalyst

The effect of on-stream sulfiding on the iso-to-normal C₄ ratio is shownin FIG. 7. In this example, a SAPO-11 catalyst was on-stream sulfidedafter 150 hours of a hydroisomerization process, and the iso-to-normalC₄ ratio plotted as a function of time. FIG. 7 illustrates thaton-stream sulfiding the catalyst resulted in the iso-to-normal C₄ ratioincreasing from about 0.2 to over 0.8, representing a more than 4-foldincrease. A higher iso-to-normal C₄ ratio indicates improved selectivityto isomerization, over cracking, reactions by the catalyst.

Example 5 Hydroisomerization Using a Pre-Sulfided SAPO Catalyst

The effect of pre-sulfiding a SAPO-11 catalyst on the amounts of lighthydrocarbons produced by hydroisomerization is shown in FIG. 8. Thetotal pressure in the reactor was 1,000 psig, and the temperature was650° F. There is a substantial reduction in the amounts of normal-C₄ andnormal-C₅, and much less of a decrease in the amounts of iso-C₄ andiso-C₅.

Example 6 Hydroisomerization Using a Pre-Sulfided SAPO Catalyst atVarying Temperature

FIGS. 9A-C illustrate some observed relationships betweenhydroisomerization temperatures and pressures. The graph in FIG. 9C is aplot of hydroisomerization temperature as a function of pour point foreach of the four runs (at total pressures of 150, 300, 500, and 1,000psig) shown in FIGS. 9A and 9B, the former figure reporting 650°F.+yield (weight percent) results, and the latter figure reportingviscosity index results. An advantage to producing lubricant base oilsat low pressure, in addition to enhanced production yields and viscosityindexes with a sulfided SAPO catalyst according to the presentembodiments, is that the hydroisomerization process may be accomplishedat significantly lower operating temperatures than otherwise would havebeen the case.

Lowering the hydroisomerization reaction temperature provides a greatertemperature range for the reaction to operate. Referring to FIG. 9C, forexample, at a pour point of −15° C., the temperature required by thecatalyst to properly hydroisomerize decreases by about 22° C. when theoperating pressure is reduced from 1,000 to 500 psig. Under analogousconditions, the required temperature is decreased by about 37° C. whenthe operating pressure is reduced from 1,000 to 300 psig. Finally, therequired temperature is decreased by about 47° C. when the operatingpressure is reduced from 1,000 to 150 psig.

All of the publications, patents and patent applications cited in thisapplication are herein incorporated by reference in their entirety tothe same extent as if the disclosure of each individual publication,patent application or patent was specifically and individually indicatedto be incorporated by reference in its entirety.

Various modifications and alterations of this invention will becomeapparent to those skilled in the art without departing from the scopeand spirit of this invention. Other objects and advantages will becomeapparent to those skilled in the art from a review of the precedingdescription. Accordingly, the invention is to be construed as includingall structure and methods that fall within the scope of the appendedclaims.

1. A method for producing a lubricant base oil from a waxy hydrocarbonfeed, the method comprising: a) pre-sulfiding a shape selective,intermediate pore size, noble metal-containing molecular sieve catalystto provide a sulfided catalyst, wherein the molar ratio of sulfur tonoble metal in the sulfided catalyst is greater than one; and b)hydroisomerizing the waxy hydrocarbon feed by contacting the waxyhydrocarbon feed with the sulfided catalyst at hydroisomerizationconditions, to produce a lubricant base oil.
 2. The method of claim 1,wherein the molar ratio of sulfur to noble metal in the sulfidedcatalyst prior to the step of hydroisomerizing is at least 2:1, andwherein the molar ratio of sulfur to noble metal in the sulfidedcatalyst during the step of hydroisomerizing is at least 3:1.
 3. Themethod of claim 1, wherein the molar ratio of sulfur to noble metal inthe sulfided catalyst is at least 3:1.
 4. The method of claim 1, whereinthe molar ratio of sulfur to noble metal in the sulfided catalyst is atleast 5:1.
 5. The method of claim 1, wherein the waxy hydrocarbon feedis selected from the group consisting of gas oil, lubricating oil stock,synthetic oil, Fischer-Tropsch derived wax, oligomerized Fischer-Tropschderived olefins, foots oil, slack wax, de-oiled wax, normal alpha olefinwax, microcrystalline wax, and mixtures thereof.
 6. The method of claim5, wherein the waxy hydrocarbon feed is a Fischer-Tropsch derived wax.7. The method of claim 1, wherein the molecular sieve has channeldiameters in the range of from about 4.0 to 7.1 Å.
 8. The method ofclaim 1, wherein the molecular sieve is non-zeolitic.
 9. The method ofclaim 8, wherein the catalyst is a SAPO catalyst.
 10. The method ofclaim 9, wherein the SAPO catalyst is selected from the group consistingof SAPO-11, SAPO-31, and SAPO-41.
 11. The method of claim 1, wherein thenoble metal is selected from the group consisting of platinum,palladium, and mixtures thereof.
 12. The method of claim 1, wherein thepre-sulfiding step comprises contacting the catalyst with asulfur-containing species in the presence of hydrogen, thesulfur-containing species being selected from the group consisting ofhydrogen sulfide, carbon disulfide, and a mercaptan.
 13. The method ofclaim 12, wherein the waxy hydrocarbon feed contains less than about 10ppm sulfur.
 14. The method of claim 1, wherein the waxy hydrocarbon feedis a sulfur spiked feedstock.
 15. The method of claim 1, wherein thehydroisomerization conditions include a total pressure of between about150 and 1,000 psig.
 16. The method of claim 15, wherein thehydroisomerization conditions include a total pressure of between about150 and 500 psig.
 17. The method of claim 16, wherein thehydroisomerization conditions include a total pressure of between about150 and 300 psig.
 18. The method of claim 15, wherein thehydroisomerization conditions include a total pressure of between about500 and 1,000 psig.
 19. The method of claim 1, wherein between about 40and 95 weight percent of the lubricant base oil has a boiling point ofbetween about 650 and 1400° F.
 20. The method of claim 1, wherein thelubricant base oil has a viscosity index between about 140 and
 190. 21.The method of claim 1, wherein the lubricant base oil has a pour pointbetween about −5 and −60° C.
 22. The method of claim 1, wherein thelubricant base oil has a viscosity at 100° C. of greater than 3 cSt. 23.The method of claim 1, further comprising solvent dewaxing at least aportion of the lubricant base oil, thereby removing a slack wax.
 24. Themethod of claim 23, further comprising hydroisomerizing the slack waxwith the waxy hydrocarbon feed.
 25. A process for producing a lubricantbase oil comprising: a) contacting a shape selective, intermediate poresize, noble-metal containing molecular sieve with a sulfur-containingspecies to provide a pre-sulfided catalyst, wherein the molar ratio ofsulfur to noble metal in the pre-sulfided catalyst is greater than one;b) providing a Fischer-Tropsch waxy hydrocarbon feed; c) contacting theFischer-Tropsch waxy hydrocarbon feed with the pre-sulfided catalyst tohydroisomerize the feed; and d) isolating a lubricant base oil.
 26. Theprocess of claim 25, wherein the lubricant base oil has a pour pointbetween about −5 and −60° C. and a viscosity index at 100° C. of greaterthan 3 cSt.